Fusion Dynamics for Hot Fusion Reactions revealed in Quasielastic Fusion Barrier Distributions

In order to clarify the fusion dynamics for hot fusion reactions, we measured the excitation functions on quasielastic (QE) scattering cross sections σ_QE for ²²Ne+²⁴⁸Cm, ²⁶Mg+²⁴⁸Cm, and ⁴⁸Ca+²³⁸U systems. In contrast to previous QE fusion barrier distribution studies which measured the recoiled projectile nuclei at backward angles (θ_lab ∼ 170◦), this work obtained successfully the σ_QE for l = 0 by measuring the target nuclei recoiling into  forward angle employing the gas-filled-type recoil ion separator GARIS. The QE fusion barrier distribution D_QE were successfully extracted, and compared with coupled-channels calculations. The calculation results clearly shows that the D_QE values are strongly affected by the deformation of the target nucleus and influenced by vibrational and rotational excitations of the colliding nuclei. Comparing the peak of the evaporation residue cross sections σ_ER with the experimental average Coulomb barrier height B₀, we found that the peaks appear well above the B₀ in the barrier distributions. This indicates that the σ_ER values are enhanced at the energy which corresponds to a compact collision geometry with the projectile impacting the side of the deformed target nucleus.